"rep" is short for "repetition." If an exercise says to do 5 reps, you're supposed to do that motion five times.
"set" I'd have to hear in context, I'm not sure what you mean by that. It could be a series of movements, like do this set six times, you'd do that series of motions six times.
Sets - How many times you do an amount of reps, spaced out by rest.
Reps - The amount of times you lift the weight in a set.
Example: I benched for 3 sets of 8-12 reps.
Also, if you're asking this question, then you need to do A LOT of research before you try a weight lifting program. And don't ask for all the answers on here. Hit up Google and check out forums on sites like elitefts.com and bodybuilding.com.